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Simple constraint exclusion. For now, only child tables of inheritance

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scans are candidates for exclusion; this should be fixed eventually.
Simon Riggs, with some help from Tom Lane.
This commit is contained in:
Tom Lane 2005-07-23 21:05:48 +00:00
parent 9af9d674c6
commit d007a95055
14 changed files with 621 additions and 105 deletions
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52
doc/src/sgml/runtime.sgml
View File

@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.338 2005/07/14 05:13:38 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.339 2005/07/23 21:05:45 tgl Exp $
-->
<chapter Id="runtime">
@ -2278,6 +2278,56 @@ archive_command = 'copy "%p" /mnt/server/archivedir/"%f"' # Windows
</listitem>
</varlistentry>
<varlistentry id="guc-enable-constraint-exclusion" xreflabel="enable_constraint_exclusion">
<term><varname>enable_constraint_exclusion</varname> (<type>boolean</type>)</term>
<indexterm>
<primary>constraint exclusion</primary>
</indexterm>
<indexterm>
<primary><varname>enable_constraint_exclusion</> configuration parameter</primary>
</indexterm>
<listitem>
<para>
Enables or disables the query planner's use of table constraints.
The default is <literal>off</>.
</para>
<para>
When this parameter is <literal>on</>, the planner compares query
conditions to table CHECK constraints, and omits scanning tables
for which the conditions contradict the constraints. (Presently
this is done only for child tables of inheritance scans.) For
example:
<programlisting>
CREATE TABLE parent(key integer, ...);
CREATE TABLE child1000(check (key between 1000 and 1999)) INHERITS(parent);
CREATE TABLE child2000(check (key between 2000 and 2999)) INHERITS(parent);
...
SELECT * FROM parent WHERE key = 2400;
</programlisting>
With constraint exclusion enabled, this SELECT will not scan
<structname>child1000</> at all. This can improve performance when
inheritance is used to build partitioned tables.
</para>
<para>
Currently, <varname>enable_constraint_exclusion</> defaults to
<literal>off</>, because it creates a risk of wrong answers when
query plans are cached: if a table constraint is changed or dropped,
the previously generated plan may now be wrong, and there is no
built-in mechanism to force re-planning. (This deficiency will
probably be addressed in a future
<productname>PostgreSQL</productname> release.) Another reason
for keeping it off is that the constraint checks are relatively
expensive to make, and in many circumstances will yield no savings.
It is recommended to turn this on only if you are actually using
partitioned tables designed to take advantage of the feature.
</para>
</listitem>
</varlistentry>
<varlistentry id="guc-from-collapse-limit" xreflabel="from_collapse_limit">
<term><varname>from_collapse_limit</varname> (<type>integer</type>)</term>
<indexterm>

40
src/backend/optimizer/path/allpaths.c
View File

@ -8,13 +8,14 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.134 2005/06/10 03:32:21 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.135 2005/07/23 21:05:46 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "nodes/makefuncs.h"
#ifdef OPTIMIZER_DEBUG
#include "nodes/print.h"
#endif
@ -25,6 +26,7 @@
#include "optimizer/paths.h"
#include "optimizer/plancat.h"
#include "optimizer/planner.h"
#include "optimizer/predtest.h"
#include "optimizer/prep.h"
#include "optimizer/var.h"
#include "parser/parsetree.h"
@ -34,6 +36,7 @@
/* These parameters are set by GUC */
bool enable_constraint_exclusion = false;
bool enable_geqo = false; /* just in case GUC doesn't set it */
int geqo_threshold;
@ -311,7 +314,37 @@ set_inherited_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
childOID);
/*
* Now compute child access paths, and save the cheapest.
* If we can prove we don't need to scan this child via constraint
* exclusion, just ignore it. (We have to have converted the
* baserestrictinfo Vars before we can make the test.)
*/
if (enable_constraint_exclusion)
{
List *constraint_pred;
constraint_pred = get_relation_constraints(childOID, childrel);
/*
* We do not currently enforce that CHECK constraints contain
* only immutable functions, so it's necessary to check here.
* We daren't draw conclusions from plan-time evaluation of
* non-immutable functions.
*/
if (!contain_mutable_functions((Node *) constraint_pred))
{
/*
* The constraints are effectively ANDed together, so we can
* just try to refute the entire collection at once. This may
* allow us to make proofs that would fail if we took them
* individually.
*/
if (predicate_refuted_by(constraint_pred,
childrel->baserestrictinfo))
continue;
}
}
/*
* Compute the child's access paths, and save the cheapest.
*/
set_plain_rel_pathlist(root, childrel, childrte);
@ -345,7 +378,8 @@ set_inherited_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
/*
* Finally, build Append path and install it as the only access path
* for the parent rel.
* for the parent rel. (Note: this is correct even if we have zero
* or one live subpath due to constraint exclusion.)
*/
add_path(rel, (Path *) create_append_path(rel, subpaths));

27
src/backend/optimizer/plan/createplan.c
View File

@ -10,7 +10,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/plan/createplan.c,v 1.194 2005/07/15 22:02:51 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/plan/createplan.c,v 1.195 2005/07/23 21:05:46 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -40,7 +40,7 @@ static List *build_relation_tlist(RelOptInfo *rel);
static bool use_physical_tlist(RelOptInfo *rel);
static void disuse_physical_tlist(Plan *plan, Path *path);
static Join *create_join_plan(PlannerInfo *root, JoinPath *best_path);
static Append *create_append_plan(PlannerInfo *root, AppendPath *best_path);
static Plan *create_append_plan(PlannerInfo *root, AppendPath *best_path);
static Result *create_result_plan(PlannerInfo *root, ResultPath *best_path);
static Material *create_material_plan(PlannerInfo *root, MaterialPath *best_path);
static Plan *create_unique_plan(PlannerInfo *root, UniquePath *best_path);
@ -435,7 +435,7 @@ create_join_plan(PlannerInfo *root, JoinPath *best_path)
*
* Returns a Plan node.
*/
static Append *
static Plan *
create_append_plan(PlannerInfo *root, AppendPath *best_path)
{
Append *plan;
@ -443,6 +443,25 @@ create_append_plan(PlannerInfo *root, AppendPath *best_path)
List *subplans = NIL;
ListCell *subpaths;
/*
* It is possible for the subplans list to contain only one entry,
* or even no entries. Handle these cases specially.
*
* XXX ideally, if there's just one entry, we'd not bother to generate
* an Append node but just return the single child. At the moment this
* does not work because the varno of the child scan plan won't match
* the parent-rel Vars it'll be asked to emit.
*/
if (best_path->subpaths == NIL)
{
/* Generate a Result plan with constant-FALSE gating qual */
return (Plan *) make_result(tlist,
(Node *) list_make1(makeBoolConst(false,
false)),
NULL);
}
/* Normal case with multiple subpaths */
foreach(subpaths, best_path->subpaths)
{
Path *subpath = (Path *) lfirst(subpaths);
@ -452,7 +471,7 @@ create_append_plan(PlannerInfo *root, AppendPath *best_path)
plan = make_append(subplans, false, tlist);
return plan;
return (Plan *) plan;
}
/*

3
src/backend/optimizer/plan/planagg.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/plan/planagg.c,v 1.5 2005/06/05 22:32:56 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/plan/planagg.c,v 1.6 2005/07/23 21:05:46 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -184,7 +184,6 @@ optimize_minmax_aggregates(PlannerInfo *root, List *tlist, Path *best_path)
*/
if (IsA(best_path, ResultPath))
{
Assert(((ResultPath *) best_path)->subpath != NULL);
constant_quals = ((ResultPath *) best_path)->constantqual;
/* no need to do this more than once: */
constant_quals = order_qual_clauses(root, constant_quals);

82
src/backend/optimizer/util/plancat.c
View File

@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.112 2005/06/13 23:14:48 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.113 2005/07/23 21:05:47 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -25,6 +25,7 @@
#include "nodes/makefuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/plancat.h"
#include "optimizer/prep.h"
#include "optimizer/tlist.h"
#include "parser/parsetree.h"
#include "parser/parse_expr.h"
@ -359,6 +360,85 @@ estimate_rel_size(Relation rel, int32 *attr_widths,
}
}
/*
* get_relation_constraints
*
* Retrieve the CHECK constraint expressions of the given relation.
*
* Returns a List (possibly empty) of constraint expressions. Each one
* has been canonicalized, and its Vars are changed to have the varno
* indicated by rel->relid. This allows the expressions to be easily
* compared to expressions taken from WHERE.
*
* Note: at present this is invoked at most once per relation per planner
* run, and in many cases it won't be invoked at all, so there seems no
* point in caching the data in RelOptInfo.
*/
List *
get_relation_constraints(Oid relationObjectId, RelOptInfo *rel)
{
List *result = NIL;
Index varno = rel->relid;
Relation relation;
TupleConstr *constr;
/*
* We assume the relation has already been safely locked.
*/
relation = heap_open(relationObjectId, NoLock);
constr = relation->rd_att->constr;
if (constr != NULL)
{
int num_check = constr->num_check;
int i;
for (i = 0; i < num_check; i++)
{
Node *cexpr;
cexpr = stringToNode(constr->check[i].ccbin);
/*
* Run each expression through const-simplification and
* canonicalization. This is not just an optimization, but is
* necessary, because we will be comparing it to
* similarly-processed qual clauses, and may fail to detect valid
* matches without this. This must match the processing done to
* qual clauses in preprocess_expression()! (We can skip the
* stuff involving subqueries, however, since we don't allow any
* in check constraints.)
*/
cexpr = eval_const_expressions(cexpr);
cexpr = (Node *) canonicalize_qual((Expr *) cexpr);
/*
* Also mark any coercion format fields as "don't care", so that
* we can match to both explicit and implicit coercions.
*/
set_coercionform_dontcare(cexpr);
/* Fix Vars to have the desired varno */
if (varno != 1)
ChangeVarNodes(cexpr, 1, varno, 0);
/*
* Finally, convert to implicit-AND format (that is, a List)
* and append the resulting item(s) to our output list.
*/
result = list_concat(result,
make_ands_implicit((Expr *) cexpr));
}
}
heap_close(relation, NoLock);
return result;
}
/*
* build_physical_tlist
*

450
src/backend/optimizer/util/predtest.c
View File

@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/util/predtest.c,v 1.1 2005/06/10 22:25:36 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/util/predtest.c,v 1.2 2005/07/23 21:05:47 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -27,7 +27,11 @@
static bool predicate_implied_by_recurse(Node *clause, Node *predicate);
static bool predicate_refuted_by_recurse(Node *clause, Node *predicate);
static bool predicate_implied_by_simple_clause(Expr *predicate, Node *clause);
static bool predicate_refuted_by_simple_clause(Expr *predicate, Node *clause);
static bool btree_predicate_proof(Expr *predicate, Node *clause,
bool refute_it);
/*
@ -35,12 +39,19 @@ static bool predicate_implied_by_simple_clause(Expr *predicate, Node *clause);
* Recursively checks whether the clauses in restrictinfo_list imply
* that the given predicate is true.
*
* The top-level List structure of each list corresponds to an AND list.
* We assume that eval_const_expressions() has been applied and so there
* are no un-flattened ANDs or ORs (e.g., no AND immediately within an AND,
* including AND just below the top-level List structure).
* If this is not true we might fail to prove an implication that is
* valid, but no worse consequences will ensue.
* The top-level List structure of each list corresponds to an AND list.
* We assume that eval_const_expressions() has been applied and so there
* are no un-flattened ANDs or ORs (e.g., no AND immediately within an AND,
* including AND just below the top-level List structure).
* If this is not true we might fail to prove an implication that is
* valid, but no worse consequences will ensue.
*
* We assume the predicate has already been checked to contain only
* immutable functions and operators. (In current use this is true
* because the predicate is part of an index predicate that has passed
* CheckPredicate().) We dare not make deductions based on non-immutable
* functions, because they might change answers between the time we make
* the plan and the time we execute the plan.
*/
bool
predicate_implied_by(List *predicate_list, List *restrictinfo_list)
@ -70,6 +81,44 @@ predicate_implied_by(List *predicate_list, List *restrictinfo_list)
return true;
}
/*
* predicate_refuted_by
* Recursively checks whether the clauses in restrictinfo_list refute
* the given predicate (that is, prove it false).
*
* This is NOT the same as !(predicate_implied_by), though it is similar
* in the technique and structure of the code.
*
* The top-level List structure of each list corresponds to an AND list.
* We assume that eval_const_expressions() has been applied and so there
* are no un-flattened ANDs or ORs (e.g., no AND immediately within an AND,
* including AND just below the top-level List structure).
* If this is not true we might fail to prove an implication that is
* valid, but no worse consequences will ensue.
*
* We assume the predicate has already been checked to contain only
* immutable functions and operators. We dare not make deductions based on
* non-immutable functions, because they might change answers between the
* time we make the plan and the time we execute the plan.
*/
bool
predicate_refuted_by(List *predicate_list, List *restrictinfo_list)
{
if (predicate_list == NIL)
return false; /* no predicate: no refutation is possible */
if (restrictinfo_list == NIL)
return false; /* no restriction: refutation must fail */
/*
* Unlike the implication case, predicate_refuted_by_recurse needs to
* be able to see the top-level AND structure on both sides --- otherwise
* it will fail to handle the case where one restriction clause is an OR
* that can refute the predicate AND as a whole, but not each predicate
* clause separately.
*/
return predicate_refuted_by_recurse((Node *) restrictinfo_list,
(Node *) predicate_list);
}
/*----------
* predicate_implied_by_recurse
@ -240,9 +289,271 @@ predicate_implied_by_recurse(Node *clause, Node *predicate)
}
}
/*----------
* predicate_refuted_by_recurse
* Does the predicate refutation test for non-NULL restriction and
* predicate clauses.
*
* The logic followed here is ("R=>" means "refutes"):
* atom A R=> atom B iff: predicate_refuted_by_simple_clause says so
* atom A R=> AND-expr B iff: A R=> any of B's components
* atom A R=> OR-expr B iff: A R=> each of B's components
* AND-expr A R=> atom B iff: any of A's components R=> B
* AND-expr A R=> AND-expr B iff: A R=> any of B's components,
* *or* any of A's components R=> B
* AND-expr A R=> OR-expr B iff: A R=> each of B's components
* OR-expr A R=> atom B iff: each of A's components R=> B
* OR-expr A R=> AND-expr B iff: each of A's components R=> any of B's
* OR-expr A R=> OR-expr B iff: A R=> each of B's components
*
* Other comments are as for predicate_implied_by_recurse(), except that
* we have to handle a top-level AND list on both sides.
*----------
*/
static bool
predicate_refuted_by_recurse(Node *clause, Node *predicate)
{
ListCell *item;
Assert(clause != NULL);
/* skip through RestrictInfo */
if (IsA(clause, RestrictInfo))
{
clause = (Node *) ((RestrictInfo *) clause)->clause;
Assert(clause != NULL);
Assert(!IsA(clause, RestrictInfo));
}
Assert(predicate != NULL);
/*
* Since a restriction List clause is handled the same as an AND clause,
* we can avoid duplicate code like this:
*/
if (and_clause(clause))
clause = (Node *) ((BoolExpr *) clause)->args;
/* Ditto for predicate AND-clause and List */
if (and_clause(predicate))
predicate = (Node *) ((BoolExpr *) predicate)->args;
if (IsA(clause, List))
{
if (IsA(predicate, List))
{
/* AND-clause R=> AND-clause if A refutes any of B's items */
/* Needed to handle (x AND y) R=> ((!x OR !y) AND z) */
foreach(item, (List *) predicate)
{
if (predicate_refuted_by_recurse(clause, lfirst(item)))
return true;
}
/* Also check if any of A's items refutes B */
/* Needed to handle ((x OR y) AND z) R=> (!x AND !y) */
foreach(item, (List *) clause)
{
if (predicate_refuted_by_recurse(lfirst(item), predicate))
return true;
}
return false;
}
else if (or_clause(predicate))
{
/* AND-clause R=> OR-clause if A refutes each of B's items */
foreach(item, ((BoolExpr *) predicate)->args)
{
if (!predicate_refuted_by_recurse(clause, lfirst(item)))
return false;
}
return true;
}
else
{
/* AND-clause R=> atom if any of A's items refutes B */
foreach(item, (List *) clause)
{
if (predicate_refuted_by_recurse(lfirst(item), predicate))
return true;
}
return false;
}
}
else if (or_clause(clause))
{
if (or_clause(predicate))
{
/* OR-clause R=> OR-clause if A refutes each of B's items */
foreach(item, ((BoolExpr *) predicate)->args)
{
if (!predicate_refuted_by_recurse(clause, lfirst(item)))
return false;
}
return true;
}
else if (IsA(predicate, List))
{
/*
* OR-clause R=> AND-clause if each of A's items refutes any of
* B's items.
*/
foreach(item, ((BoolExpr *) clause)->args)
{
Node *citem = lfirst(item);
ListCell *item2;
foreach(item2, (List *) predicate)
{
if (predicate_refuted_by_recurse(citem, lfirst(item2)))
break;
}
if (item2 == NULL)
return false; /* citem refutes nothing */
}
return true;
}
else
{
/* OR-clause R=> atom if each of A's items refutes B */
foreach(item, ((BoolExpr *) clause)->args)
{
if (!predicate_refuted_by_recurse(lfirst(item), predicate))
return false;
}
return true;
}
}
else
{
if (IsA(predicate, List))
{
/* atom R=> AND-clause if A refutes any of B's items */
foreach(item, (List *) predicate)
{
if (predicate_refuted_by_recurse(clause, lfirst(item)))
return true;
}
return false;
}
else if (or_clause(predicate))
{
/* atom R=> OR-clause if A refutes each of B's items */
foreach(item, ((BoolExpr *) predicate)->args)
{
if (!predicate_refuted_by_recurse(clause, lfirst(item)))
return false;
}
return true;
}
else
{
/* atom R=> atom is the base case */
return predicate_refuted_by_simple_clause((Expr *) predicate,
clause);
}
}
}
/*----------
* predicate_implied_by_simple_clause
* Does the predicate implication test for a "simple clause" predicate
* and a "simple clause" restriction.
*
* We return TRUE if able to prove the implication, FALSE if not.
*
* We have three strategies for determining whether one simple clause
* implies another:
*
* A simple and general way is to see if they are equal(); this works for any
* kind of expression. (Actually, there is an implied assumption that the
* functions in the expression are immutable, ie dependent only on their input
* arguments --- but this was checked for the predicate by the caller.)
*
* When the predicate is of the form "foo IS NOT NULL", we can conclude that
* the predicate is implied if the clause is a strict operator or function
* that has "foo" as an input. In this case the clause must yield NULL when
* "foo" is NULL, which we can take as equivalent to FALSE because we know
* we are within an AND/OR subtree of a WHERE clause. (Again, "foo" is
* already known immutable, so the clause will certainly always fail.)
*
* Finally, we may be able to deduce something using knowledge about btree
* operator classes; this is encapsulated in btree_predicate_proof().
*----------
*/
static bool
predicate_implied_by_simple_clause(Expr *predicate, Node *clause)
{
/* First try the equal() test */
if (equal((Node *) predicate, clause))
return true;
/* Next try the IS NOT NULL case */
if (predicate && IsA(predicate, NullTest) &&
((NullTest *) predicate)->nulltesttype == IS_NOT_NULL)
{
Expr *nonnullarg = ((NullTest *) predicate)->arg;
if (is_opclause(clause) &&
list_member(((OpExpr *) clause)->args, nonnullarg) &&
op_strict(((OpExpr *) clause)->opno))
return true;
if (is_funcclause(clause) &&
list_member(((FuncExpr *) clause)->args, nonnullarg) &&
func_strict(((FuncExpr *) clause)->funcid))
return true;
return false; /* we can't succeed below... */
}
/* Else try btree operator knowledge */
return btree_predicate_proof(predicate, clause, false);
}
/*----------
* predicate_refuted_by_simple_clause
* Does the predicate refutation test for a "simple clause" predicate
* and a "simple clause" restriction.
*
* We return TRUE if able to prove the refutation, FALSE if not.
*
* Unlike the implication case, checking for equal() clauses isn't
* helpful. (XXX is it worth looking at "x vs NOT x" cases? Probably
* not seeing that canonicalization tries to get rid of NOTs.)
*
* When the predicate is of the form "foo IS NULL", we can conclude that
* the predicate is refuted if the clause is a strict operator or function
* that has "foo" as an input. See notes for implication case.
*
* Finally, we may be able to deduce something using knowledge about btree
* operator classes; this is encapsulated in btree_predicate_proof().
*----------
*/
static bool
predicate_refuted_by_simple_clause(Expr *predicate, Node *clause)
{
/* First try the IS NULL case */
if (predicate && IsA(predicate, NullTest) &&
((NullTest *) predicate)->nulltesttype == IS_NULL)
{
Expr *isnullarg = ((NullTest *) predicate)->arg;
if (is_opclause(clause) &&
list_member(((OpExpr *) clause)->args, isnullarg) &&
op_strict(((OpExpr *) clause)->opno))
return true;
if (is_funcclause(clause) &&
list_member(((FuncExpr *) clause)->args, isnullarg) &&
func_strict(((FuncExpr *) clause)->funcid))
return true;
return false; /* we can't succeed below... */
}
/* Else try btree operator knowledge */
return btree_predicate_proof(predicate, clause, true);
}
/*
* Define an "operator implication table" for btree operators ("strategies").
* Define an "operator implication table" for btree operators ("strategies"),
* and a similar table for refutation.
*
* The strategy numbers defined by btree indexes (see access/skey.h) are:
* (1) < (2) <= (3) = (4) >= (5) >
@ -263,8 +574,21 @@ predicate_implied_by_recurse(Node *clause, Node *predicate)
* then the target expression must be true; if the test returns false, then
* the target expression may be false.
*
* An entry where test_op == 0 means the implication cannot be determined,
* i.e., this test should always be considered false.
* For example, if clause is "Quantity > 10" and pred is "Quantity > 5"
* then we test "5 <= 10" which evals to true, so clause implies pred.
*
* Similarly, the interpretation of a BT_refute_table entry is:
*
* If you know, for some ATTR, that "ATTR given_op CONST1" is true, and you
* want to determine whether "ATTR target_op CONST2" must be false, then
* you can use "CONST2 test_op CONST1" as a test. If this test returns true,
* then the target expression must be false; if the test returns false, then
* the target expression may be true.
*
* For example, if clause is "Quantity > 10" and pred is "Quantity < 5"
* then we test "5 <= 10" which evals to true, so clause refutes pred.
*
* An entry where test_op == 0 means the implication cannot be determined.
*/
#define BTLT BTLessStrategyNumber
@ -274,58 +598,60 @@ predicate_implied_by_recurse(Node *clause, Node *predicate)
#define BTGT BTGreaterStrategyNumber
#define BTNE 6
static const StrategyNumber
BT_implic_table[6][6] = {
static const StrategyNumber BT_implic_table[6][6] = {
/*
* The target operator:
*
* LT LE EQ GE GT NE
* LT LE EQ GE GT NE
*/
{BTGE, BTGE, 0, 0, 0, BTGE}, /* LT */
{BTGT, BTGE, 0, 0, 0, BTGT}, /* LE */
{BTGE, BTGE, 0 , 0 , 0 , BTGE}, /* LT */
{BTGT, BTGE, 0 , 0 , 0 , BTGT}, /* LE */
{BTGT, BTGE, BTEQ, BTLE, BTLT, BTNE}, /* EQ */
{0, 0, 0, BTLE, BTLT, BTLT}, /* GE */
{0, 0, 0, BTLE, BTLE, BTLE}, /* GT */
{0, 0, 0, 0, 0, BTEQ} /* NE */
{0 , 0 , 0 , BTLE, BTLT, BTLT}, /* GE */
{0 , 0 , 0 , BTLE, BTLE, BTLE}, /* GT */
{0 , 0 , 0 , 0 , 0 , BTEQ} /* NE */
};
static const StrategyNumber BT_refute_table[6][6] = {
/*
* The target operator:
*
* LT LE EQ GE GT NE
*/
{0 , 0 , BTGE, BTGE, BTGE, 0 }, /* LT */
{0 , 0 , BTGT, BTGT, BTGE, 0 }, /* LE */
{BTLE, BTLT, BTNE, BTGT, BTGE, BTEQ}, /* EQ */
{BTLE, BTLT, BTLT, 0 , 0 , 0 }, /* GE */
{BTLE, BTLE, BTLE, 0 , 0 , 0 }, /* GT */
{0 , 0 , BTEQ, 0 , 0 , 0 } /* NE */
};
/*----------
* predicate_implied_by_simple_clause
* Does the predicate implication test for a "simple clause" predicate
* and a "simple clause" restriction.
* btree_predicate_proof
* Does the predicate implication or refutation test for a "simple clause"
* predicate and a "simple clause" restriction, when both are simple
* operator clauses using related btree operators.
*
* We have three strategies for determining whether one simple clause
* implies another:
* When refute_it == false, we want to prove the predicate true;
* when refute_it == true, we want to prove the predicate false.
* (There is enough common code to justify handling these two cases
* in one routine.) We return TRUE if able to make the proof, FALSE
* if not able to prove it.
*
* A simple and general way is to see if they are equal(); this works for any
* kind of expression. (Actually, there is an implied assumption that the
* functions in the expression are immutable, ie dependent only on their input
* arguments --- but this was checked for the predicate by CheckPredicate().)
*
* When the predicate is of the form "foo IS NOT NULL", we can conclude that
* the predicate is implied if the clause is a strict operator or function
* that has "foo" as an input. In this case the clause must yield NULL when
* "foo" is NULL, which we can take as equivalent to FALSE because we know
* we are within an AND/OR subtree of a WHERE clause. (Again, "foo" is
* already known immutable, so the clause will certainly always fail.)
*
* Our other way works only for binary boolean opclauses of the form
* What we look for here is binary boolean opclauses of the form
* "foo op constant", where "foo" is the same in both clauses. The operators
* and constants can be different but the operators must be in the same btree
* operator class. We use the above operator implication table to be able to
* operator class. We use the above operator implication tables to
* derive implications between nonidentical clauses. (Note: "foo" is known
* immutable, and constants are surely immutable, but we have to check that
* the operators are too. As of 8.0 it's possible for opclasses to contain
* operators that are merely stable, and we dare not make deductions with
* these.)
*
* Eventually, rtree operators could also be handled by defining an
* appropriate "RT_implic_table" array.
*----------
*/
static bool
predicate_implied_by_simple_clause(Expr *predicate, Node *clause)
btree_predicate_proof(Expr *predicate, Node *clause, bool refute_it)
{
Node *leftop,
*rightop;
@ -356,29 +682,8 @@ predicate_implied_by_simple_clause(Expr *predicate, Node *clause)
EState *estate;
MemoryContext oldcontext;
/* First try the equal() test */
if (equal((Node *) predicate, clause))
return true;
/* Next try the IS NOT NULL case */
if (predicate && IsA(predicate, NullTest) &&
((NullTest *) predicate)->nulltesttype == IS_NOT_NULL)
{
Expr *nonnullarg = ((NullTest *) predicate)->arg;
if (is_opclause(clause) &&
list_member(((OpExpr *) clause)->args, nonnullarg) &&
op_strict(((OpExpr *) clause)->opno))
return true;
if (is_funcclause(clause) &&
list_member(((FuncExpr *) clause)->args, nonnullarg) &&
func_strict(((FuncExpr *) clause)->funcid))
return true;
return false; /* we can't succeed below... */
}
/*
* Can't do anything more unless they are both binary opclauses with a
* Both expressions must be binary opclauses with a
* Const on one side, and identical subexpressions on the other sides.
* Note we don't have to think about binary relabeling of the Const
* node, since that would have been folded right into the Const.
@ -579,7 +884,11 @@ predicate_implied_by_simple_clause(Expr *predicate, Node *clause)
/*
* Look up the "test" strategy number in the implication table
*/
test_strategy = BT_implic_table[clause_strategy - 1][pred_strategy - 1];
if (refute_it)
test_strategy = BT_refute_table[clause_strategy - 1][pred_strategy - 1];
else
test_strategy = BT_implic_table[clause_strategy - 1][pred_strategy - 1];
if (test_strategy == 0)
{
/* Can't determine implication using this interpretation */
@ -608,13 +917,10 @@ predicate_implied_by_simple_clause(Expr *predicate, Node *clause)
* Last check: test_op must be immutable.
*
* Note that we require only the test_op to be immutable, not the
* original clause_op. (pred_op must be immutable, else it
* would not be allowed in an index predicate.) Essentially
* we are assuming that the opclass is consistent even if it
* contains operators that are merely stable.
*
* XXX the above reasoning doesn't hold anymore if this routine
* is used to prove things that are not index predicates ...
* original clause_op. (pred_op is assumed to have been checked
* immutable by the caller.) Essentially we are assuming that
* the opclass is consistent even if it contains operators that
* are merely stable.
*/
if (op_volatile(test_op) == PROVOLATILE_IMMUTABLE)
{
@ -663,7 +969,7 @@ predicate_implied_by_simple_clause(Expr *predicate, Node *clause)
if (isNull)
{
/* Treat a null result as false ... but it's a tad fishy ... */
/* Treat a null result as non-proof ... but it's a tad fishy ... */
elog(DEBUG2, "null predicate test result");
return false;
}

12
src/backend/utils/misc/guc.c
View File

@ -10,7 +10,7 @@
* Written by Peter Eisentraut <peter_e@gmx.net>.
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.276 2005/07/21 18:06:12 momjian Exp $
* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.277 2005/07/23 21:05:47 tgl Exp $
*
*--------------------------------------------------------------------
*/
@ -435,6 +435,16 @@ static struct config_bool ConfigureNamesBool[] =
&enable_hashjoin,
true, NULL, NULL
},
{
{"enable_constraint_exclusion", PGC_USERSET, QUERY_TUNING_OTHER,
gettext_noop("Enables the planner's use of constraints in queries."),
gettext_noop("Constraints will be examined to exclude tables "
"that can be proven not to be required to produce "
"a correct result for the query.")
},
&enable_constraint_exclusion,
false, NULL, NULL
},
{
{"geqo", PGC_USERSET, QUERY_TUNING_GEQO,
gettext_noop("Enables genetic query optimization."),

1
src/backend/utils/misc/postgresql.conf.sample
View File

@ -173,6 +173,7 @@
# - Other Planner Options -
#default_statistics_target = 10 # range 1-1000
#enable_constraint_exclusion = off
#from_collapse_limit = 8
#join_collapse_limit = 8 # 1 disables collapsing of explicit JOINs

3
src/bin/psql/tab-complete.c
View File

@ -3,7 +3,7 @@
*
* Copyright (c) 2000-2005, PostgreSQL Global Development Group
*
* $PostgreSQL: pgsql/src/bin/psql/tab-complete.c,v 1.133 2005/06/22 21:14:30 tgl Exp $
* $PostgreSQL: pgsql/src/bin/psql/tab-complete.c,v 1.134 2005/07/23 21:05:47 tgl Exp $
*/
/*----------------------------------------------------------------------
@ -540,6 +540,7 @@ psql_completion(char *text, int start, int end)
"dynamic_library_path",
"effective_cache_size",
"enable_bitmapscan",
"enable_constraint_exclusion",
"enable_hashagg",
"enable_hashjoin",
"enable_indexscan",

20
src/include/nodes/relation.h
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.116 2005/07/02 23:00:42 tgl Exp $
* $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.117 2005/07/23 21:05:48 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -516,6 +516,9 @@ typedef struct TidPath
* AppendPath represents an Append plan, ie, successive execution of
* several member plans. Currently it is only used to handle expansion
* of inheritance trees.
*
* Note: it is possible for "subpaths" to contain only one, or even no,
* elements. These cases are optimized during create_append_plan.
*/
typedef struct AppendPath
{
@ -524,10 +527,17 @@ typedef struct AppendPath
} AppendPath;
/*
* ResultPath represents use of a Result plan node, either to compute a
* variable-free targetlist or to gate execution of a subplan with a
* one-time (variable-free) qual condition. Note that in the former case
* path.parent will be NULL; in the latter case it is copied from the subpath.
* ResultPath represents use of a Result plan node. There are several
* applications for this:
* * To compute a variable-free targetlist (a "SELECT expressions" query).
* In this case subpath and path.parent will both be NULL. constantqual
* might or might not be empty ("SELECT expressions WHERE something").
* * To gate execution of a subplan with a one-time (variable-free) qual
* condition. path.parent is copied from the subpath.
* * To substitute for a scan plan when we have proven that no rows in
* a table will satisfy the query. subpath is NULL but path.parent
* references the not-to-be-scanned relation, and constantqual is
* a constant FALSE.
*
* Note that constantqual is a list of bare clauses, not RestrictInfos.
*/

3
src/include/optimizer/cost.h
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/optimizer/cost.h,v 1.68 2005/06/05 22:32:58 tgl Exp $
* $PostgreSQL: pgsql/src/include/optimizer/cost.h,v 1.69 2005/07/23 21:05:48 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -49,6 +49,7 @@ extern bool enable_hashagg;
extern bool enable_nestloop;
extern bool enable_mergejoin;
extern bool enable_hashjoin;
extern bool enable_constraint_exclusion;
extern double clamp_row_est(double nrows);
extern void cost_seqscan(Path *path, PlannerInfo *root, RelOptInfo *baserel);

4
src/include/optimizer/plancat.h
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/optimizer/plancat.h,v 1.36 2005/06/05 22:32:58 tgl Exp $
* $PostgreSQL: pgsql/src/include/optimizer/plancat.h,v 1.37 2005/07/23 21:05:48 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -19,6 +19,8 @@
extern void get_relation_info(Oid relationObjectId, RelOptInfo *rel);
extern List *get_relation_constraints(Oid relationObjectId, RelOptInfo *rel);
extern List *build_physical_tlist(PlannerInfo *root, RelOptInfo *rel);
extern List *find_inheritance_children(Oid inhparent);

4
src/include/optimizer/predtest.h
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/optimizer/predtest.h,v 1.1 2005/06/10 22:25:37 tgl Exp $
* $PostgreSQL: pgsql/src/include/optimizer/predtest.h,v 1.2 2005/07/23 21:05:48 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -19,5 +19,7 @@
extern bool predicate_implied_by(List *predicate_list,
List *restrictinfo_list);
extern bool predicate_refuted_by(List *predicate_list,
List *restrictinfo_list);
#endif /* PREDTEST_H */

25
src/test/regress/expected/rangefuncs.out
View File

@ -1,16 +1,17 @@
SELECT name, setting FROM pg_settings WHERE name LIKE 'enable%';
name | setting
-------------------+---------
enable_bitmapscan | on
enable_hashagg | on
enable_hashjoin | on
enable_indexscan | on
enable_mergejoin | on
enable_nestloop | on
enable_seqscan | on
enable_sort | on
enable_tidscan | on
(9 rows)
name | setting
-----------------------------+---------
enable_bitmapscan | on
enable_constraint_exclusion | off
enable_hashagg | on
enable_hashjoin | on
enable_indexscan | on
enable_mergejoin | on
enable_nestloop | on
enable_seqscan | on
enable_sort | on
enable_tidscan | on
(10 rows)
CREATE TABLE foo2(fooid int, f2 int);
INSERT INTO foo2 VALUES(1, 11);